This invention relates to control mechanism for crossed light beam scanning of display surfaces and in particular to the mechanism controlling the sequence of emitters and detectors activated for determining the position of an object placed in proximity to the display surface.
Sequentially scanned crossed light beam position indicators are known in the prior art for detecting and transmitting the address of interrupted light beams. These indicators have utilized paired emitters and detectors in X and Y coordinate arrays such that during the time that a single emitter is activated only a single corresponding detector is activated. Examples of such address indicators for display surfaces may be found in U.S. Pat. Nos. 3,860,754; 3,775,560 and 3,764,813. In such prior art apparatus, in order to increase the resolution of the position of an object placed in proximity to the display surface, it is necessary to increase the number of emitters and detectors in the coordinate arrays.